More and more instruments are being replaced with autonomous and semiautonomous devices. This is especially true in the hospitals of today with large arrays of autonomous and semiautonomous medical devices being found in operating rooms, interventional suites, intensive care wards, emergency rooms, and/or the like. For example, glass and mercury thermometers are being replaced with electronic thermometers, intravenous drip lines now include electronic monitors and flow regulators, and traditional hand-held surgical instruments are being replaced by computer-assisted medical devices.
These medical devices provide both advantages and challenges to the personnel operating them. Many of these medical devices may be capable of autonomous or semiautonomous motion of one or more repositionable arms and/or end effectors. It is also common to operate the medical devices via teleoperation using one or more input controls on an operator workstation to control the motion and/or operation of the repositionable arms and/or the end effectors. Examples of such devices include the da Vinci® Surgical System commercialized by Intuitive Surgical, Inc. of Sunnyvale, Calif. When the medical device is operated remotely from the operator workstation and/or the end effectors are being used in an area not directly visible to the operator, such as during computer-assisted surgery when the end effectors are hidden by patient anatomy, surgical drapes, and/or the like, it may complicate the operator's ability to detect and/or avoid collisions between the one or more repositionable arms that could result in damage to the medical device, injury to a patient or other personnel, and/or failures in a sterile field.
Collision avoidance between repositionable devices, such as the repositionable arms of a medical device, is typically addressed in a motion planning context. In this context, the motion plans for each of the repositionable arms are determined, and the future motions of the repositionable arms are evaluated to determine whether collisions between the repositionable arms will occur, with appropriate corrections to the motion plans occurring to avoid the collision. This approach is often far from ideal for repositionable arms controlled via teleoperation because control of the repositionable arms is directed in real-time by an operator (i.e., the operator is unable to perceive a delay between making an input and the resulting movement) so that motion plans for the repositionable arms are not known and cannot serve as the basis for collision avoidance determinations. As an alternative to collision avoidance, a collision detection approach may be used that provides feedback to the operator when a collision occurs between the repositionable arms. But, a collision detection approach suffers disadvantages. Actual collisions often result in a poor user experience for the operator. And, at a minimum, collision detection between arms often detects the collision too late to avoid damage to the sterile field, because the sterile drapes covering the arms typically contact each other before the repositionable arms collide, and a drape trapped between two colliding arms may be torn. Some hybrid collision avoidance-collision detection systems operate by modeling large volumes, typically with planar surfaces and which are often convex in shape, that circumscribe the links and joints of the repositionable arms. In some cases, the links and joints of the repositionable arm are divided into segments with each segment having its own three-dimensional circumscribing primitive, such as a sphere, cylinder, or box, with an overall circumscribing volume being constructed by taking a union of the circumscribing primitives. As the repositionable arms are operated, collision detection is applied to the circumscribing volumes so that “collisions” between the circumscribing volumes are detected and reacted to prior to an actual collision occurring. Other approaches include providing separate non-intersecting workspaces for each of the repositionable arms that eliminate the need for additional collision detection or avoidance. These hybrid approaches, however, are often too conservative in predicting collisions as the circumscribing volumes are often overly large for the circumscribed links and joints and these overly large circumscribing volumes as well as the separate workspaces often interfere with the ability to operate the repositionable arms with separation distances smaller than the circumscribing volumes.
Accordingly, improved methods and systems for avoid collisions between the repositionable arms of computer-assisted medical devices are desirable.